The present invention relates to a system for determining normal operating values of plant data which sequentially change in the transient operational mode, for example, during the start-up or shut-down operation of a plant.
In order to determine whether or not a plant is operating normally, it is a required task for the plant operator to compare the present values of main plant data with their normal operating values. Especially, such a determination is important during any transient operational mode of the plant, since the plant status sometimes becomes unstable at such times.
In the transient operational mode, the values of the main plant data change broadly. For example, during the start-up operation of a nuclear power plant, plant data such as the reactor pressure, the reactor power, the main steam flow, and the feedwater flow are known to change in a range from 0 to 100 percent. Therefore, the operator of the plant must determine the normal values of plant data in response to the present plant status before making a comparison between the present values and the normal values. The normal value corresponds to a plant data operating value of the plant when the plant is properly operating during an operating step thereof. Even for the experienced operator, great effort and skill are required to determine the normal values of the plant data which are changing over such a wide range of values during the transient operational mode.
It is possible to determine the normal values of plant data by repeatedly analyzing the dynamic characteristic of the plant. However, such a method consumes considerable time and requires the use of rather complicated apparatus. It is, therefore, generally undesirable.